Facial Surface Electromyography Research Articles

Facial Surface Electromyography: A Novel Approach to Facial Nerve Functional Evaluation after Vestibular Schwannoma Surgery.

Vestibular schwannoma (VS) surgery may cause facial nerve damage. However, a comprehensive evaluation of post-operative facial outcomes may be difficult to achieve. Surface electromyography (sEMG) is a promising non-invasive evaluation tool. However, its use in the follow-up after VS surgery has not been reported yet. The main objective was to develop and validate a new sEMG application specifically for the post-VS surgery setting. Secondary goals were to provide a systematic description of facial muscle activity after VS surgery and assess the association between sEMG parameters and Sunnybrook scale scores. Thirty-three patients with facial palsy following VS surgery were included. The clinical outcomes (Sunnybrook symmetry, movement, and synkinesis scores) and sEMG parameters (signal amplitude normalized by the maximal voluntary contraction (NEMG) and sEMG synkinesis score (ESS, number of synkinesis per movement sequence)) were evaluated at the end of the follow-up. In all tested muscles, NEMG variance was significantly higher on the affected side than the contralateral (variance ratio test, p < 0.00001 for each muscle). In total, 30 out of 33 patients (90.9%) showed an ESS ≥ 1 (median: 2.5, IQR: 1.5-3.0). On the affected side, NEMG values positively correlated with both dynamic and overall Sunnybrook scores (Spearman's model, p < 0.05 for each muscle, except orbicularis oculi). ESS significantly correlated with the Sunnybrook synkinesis score (Spearman's rho: 0.8268, p < 0.0001). We described and preliminarily validated a novel multiparametric sEMG approach based on both signal amplitude and synkinesis evaluation specifically for oto-neurosurgery. Large-scale studies are mandatory to further characterize the semiological and prognostic value of facial sEMG.

High-resolution surface electromyographic activities of facial muscles during the six basic emotional expressions in healthy adults: a prospective observational study

High-resolution facial surface electromyography (HR-sEMG) is suited to discriminate between different facial movements. Whether HR-sEMG also allows a discrimination among the six basic emotions of facial expression is unclear. 36 healthy participants (53% female, 18–67 years) were included for four sessions. Electromyograms were recorded from both sides of the face using a muscle-position oriented electrode application (Fridlund scheme) and by a landmark-oriented, muscle unrelated symmetrical electrode arrangement (Kuramoto scheme) simultaneously on the face. In each session, participants expressed the six basic emotions in response to standardized facial images expressing the corresponding emotions. This was repeated once on the same day. Both sessions were repeated two weeks later to assess repetition effects. HR-sEMG characteristics showed systematic regional distribution patterns of emotional muscle activation for both schemes with very low interindividual variability. Statistical discrimination between the different HR-sEMG patterns was good for both schemes for most but not all basic emotions (ranging from p > 0.05 to mostly p < 0.001) when using HR-sEMG of the entire face. When using information only from the lower face, the Kuramoto scheme allowed a more reliable discrimination of all six emotions (all p < 0.001). A landmark-oriented HR-sEMG recording allows specific discrimination of facial muscle activity patterns during basic emotional expressions.

Parallel-Inception CNN Approach for Facial sEMG based Silent Speech Recognition.

With the purpose of providing an external human-machine interaction platform for the elderly in need, a novel facial surface electromyography based silent speech recognition system was developed. In this study, we propose a deep learning architecture named Parallel-Inception Convolutional Neural Network (PICNN), and employ up-to-date feature extraction method log Mel frequency spectral coefficients (MFSC). To better meet the requirements of our target users, a 100-class dataset containing daily life-related demands was designed and generated for the comparative experiments. According to experimental results, the highest recognition accuracy of 88.44% was achieved by proposed recognition framework based on MFSC and PICNN, exceeding the performance of state-of-the-art deep learning algorithms such as CNN, VGGNet and Inception CNN (3.22%, 4.09% and 1.19%, respectively). These findings suggest that the newly developed silent speech approach holds promise to provide a more reliable communication channel, and the application scenery of speech recognition technology has been expanded at the same time.

Integrated Head-Tilt and Electromyographic Cursor Control.

This study evaluated the performance of two alternate computer access methods that could be used for two-dimensional cursor control. The first method, ACC/sEMG, integrates head acceleration and facial surface electromyography. The second method, Camera Mouse, is a free-to-use, computer vision-based access method. Twenty-four healthy adults performed a target acquisition task using each computer access method across two lighting conditions and three computer orientations. Performance in the task was evaluated using metrics of target selection accuracy, movement time, and path efficiency. Using ACC/sEMG resulted in better mean path efficiency and target selection accuracy, whereas using Camera Mouse resulted in faster target selection. Moreover, performance in the task when using Camera Mouse depended on lighting conditions in the room. The findings of this study show that the ACC/sEMG system is an effective computer access method across different lighting conditions and computer orientations. However, there is a tradeoff between speed and accuracy: ACC/sEMG system provided higher target selection accuracy compared to Camera Mouse, while the latter provided faster target selection. Future development should focus on evaluating performance of each method in populations with limited motor abilities.

Objective assessment of blinking and facial expressions in Parkinson’s disease using a vertical electro-oculogram and facial surface electromyography

Objective: Hypomimia is a common and early symptom of Parkinson’s disease (PD), which reduces the ability of PD patients to manifest emotions. Currently, it is visually evaluated by the neurologist during neurological examinations for PD diagnosis, as described in task 3.2 of the Movement Disorder Society—Unified Parkinson’s Disease Rating Scale (MDS-UPDRS). Since such an evaluation is semi-quantitative and affected by inter-variability, this paper aims to measure the physiological parameters related to eye blink and facial expressions extracted from a vertical electro-oculogram (VEOG) and facial surface electromyography (fsEMG) to differentiate PD patients from healthy control subjects (HCs). Approach: The spontaneous eye blink rate-minute (sEBR), its maximum amplitude (BMP), and facial cutaneous muscle activity were measured in 24 PD patients and 24 HCs while the subjects looked at a visual-tester composed of three main parts: static vision, dynamic vision and reading silently. Specificity and sensitivity for each parameter were calculated. Main results: The VEOG and the fsEMG allowed the identification of some parameters related to eye blink and facial expressions (i.e. sEBR, BMP, frontal and peribuccal muscular activities), being able to distinguish between PD patients and HCs with high sensitivity and specificity. Significance: The demonstration that the combination of parameters related to eye blink and facial expressions can discriminate (with high accuracy) between PD patients versus HCs, thus resulting in a useful tool to support the neurologist in objective assessment of hypomimia for improving PD diagnosis.

A Wearable High-Resolution Facial Electromyography for Long Term Recordings in Freely Behaving Humans

Human facial expressions are a complex capacity, carrying important psychological and neurological information. Facial expressions typically involve the co-activation of several muscles; they vary between individuals, between voluntary versus spontaneous expressions, and depend strongly on personal interpretation. Accordingly, while high-resolution recording of muscle activation in a non-laboratory setting offers exciting opportunities, it remains a major challenge. This paper describes a wearable and non-invasive method for objective mapping of facial muscle activation and demonstrates its application in a natural setting. We focus on muscle activation associated with “enjoyment”, “social” and “masked” smiles; three categories with distinct social meanings. We use an innovative, dry, soft electrode array designed specifically for facial surface electromyography recording, a customized independent component analysis algorithm, and a short training procedure to achieve the desired mapping. First, identification of the orbicularis oculi and the levator labii superioris was demonstrated from voluntary expressions. Second, the zygomaticus major was identified from voluntary and spontaneous Duchenne and non-Duchenne smiles. Finally, using a wireless device in an unmodified work environment revealed expressions of diverse emotions in face-to-face interaction. Our high-resolution and crosstalk-free mapping, along with excellent user-convenience, opens new opportunities in gaming, virtual-reality, bio-feedback and objective psychological and neurological assessment.

Difference between Right and Left Facial Surface Electromyography in Healthy People.

Introduction The study was to see whether there were differences in values of facial surface electromyography in subjects of good heath by muscles, age, and sex. Methods It draws ratio between lower value and higher value (R-LV/HV) and asymmetry index (AI), based on root mean square (RMS) from measurement of facial surface electromyography (sEMG) in 154 people of healthy people (male:female = 70:84) aging between more than 20 and less than 70. Results For R-LV/HV, it averages 81.70±14.60% on frontalis muscle, 73.74±19.12% on zygomaticus muscle, and 79.72±14.77% on orbicularis oris muscle. With analysis of the AI average was 10.87±10.14% on frontalis muscle, 16.71±14.79% on zygomaticus muscle, and 12.10±10.05% on orbicularis oris muscle. Both values were statistically significant in three parts of muscles as shown. Both of R-LV/HV and AI show no statistically significant difference on age and sex (p>0.05). Conclusions It could provide basic data for the future diagnosis of facial nerve palsy patients by measuring facial sEMG values for healthy people.

EMG-to-Speech: Direct Generation of Speech From Facial Electromyographic Signals

Silent speech interfaces are systems that enable speech communication even when an acoustic signal is unavailable. Over the last years, public interest in such interfaces has intensified. They provide solutions for some of the challenges faced by today's speech-driven technologies, such as robustness to noise and usability for people with speech impediments. In this paper, we provide an overview over our silent speech interface. It is based on facial surface electromyography (EMG) , which we use to record the electrical signals that control muscle contraction during speech production. These signals are then converted directly to an audible speech waveform, retaining important paralinguistic speech cues for information such as speaker identity and mood. This paper gives an overview over our state-of-the-art direct EMG-to-speech transformation system. This paper describes the characteristics of the speech EMG signal, introduces techniques for extracting relevant features, presents different EMG-to-speech mapping methods, and finally, presents an evaluation of the different methods for real-time capability and conversion quality.

A Study of the Electrical Properties of the Buccal Area using Facial Surface Electromyography※

Objectives : The purpose of this study was to determine the electrical properties of the buccal area using facial surface electromyography (sEMG). Methods : This research was conducted on 44 healthy participants irrespective of their sex. Surface electrodes were attached to the midpoints of three imaginary lines connecting ST4 (Dicang) to ST6 (Jiache), ST4 to SI18 (Quanliao), and ST4 to the center point of SI18 and ST6. Then, the participants were trained in the movement that included a comprehensive action of buccal area. While the participants were performing the motion, sEMG values (E1, E2, E3) and the distance change of the three imaginary lines (D1, D2, D3) were measured. The data were statistically analyzed using SPSS ver. 22.0. Results : Significant differences were observed in the distance changes (D1>D3, D2>D3) and sEMG values (E1<E2<E3). Moreover, there were positive correlations between D1 and E1, D2 and E2. Conclusion : We suggest that the measurement at ST4 to the center point of ST6 and SI18 with this motion would be adequate to check the electrical characteristics of the buccal area.

Assessment of Emotional Expressions after Full-Face Transplantation.

We assessed clinical features as well as sensory and motor recoveries in 3 full-face transplantation patients. A frequency analysis was performed on facial surface electromyography data collected during 6 basic emotional expressions and 4 primary facial movements. Motor progress was assessed using the wavelet packet method by comparison against the mean results obtained from 10 healthy subjects. Analyses were conducted on 1 patient at approximately 1 year after face transplantation and at 2 years after transplantation in the remaining 2 patients. Motor recovery was observed following sensory recovery in all 3 patients; however, the 3 cases had different backgrounds and exhibited different degrees and rates of sensory and motor improvements after transplant. Wavelet packet energy was detected in all patients during emotional expressions and primary movements; however, there were fewer active channels during expressions in transplant patients compared to healthy individuals, and patterns of wavelet packet energy were different for each patient. Finally, high-frequency components were typically detected in patients during emotional expressions, but fewer channels demonstrated these high-frequency components in patients compared to healthy individuals. Our data suggest that the posttransplantation recovery of emotional facial expression requires neural plasticity.

Discrete and continuous auditory feedback based on pitch and spatial lateralization for human-machine-interface control

The purpose of this study was to investigate auditory-motor learning via discrete and continuous auditory feedback using pitch and spatial lateralization. Sixteen subjects used facial surface electromyography (sEMG) to control a human-machine-interface (HMI). The output of the HMI was a lateralized harmonic tone. The fundamental frequency and lateralization (left-right ear) changed with the sum and the difference of the bilateral muscle signals. For eight participants, these changes were continuous, whereas the other eight participants received discrete feedback, in which the frequency of the tone was one of nine possible semitones (from midi note #64 to #75) and the lateralization was either left, center or right. Participants trained over three days. A mixed-models analysis of variance showed a significant effect of learning over sessions and a trend for increased performance for the group utilizing discrete feedback. Overall, information transfer rates using this purely auditory feedback averaged 38.5 bit/min by day 3, which is similar to results from similar systems utilizing visual feedback. These results show that with minimal training, auditory feedback can provide usable HMI control.

Effects of augmentative visual training on audio-motor mapping

The purpose of this study was to determine the effect of augmentative visual feedback training on auditory–motor performance. Thirty-two healthy young participants used facial surface electromyography (sEMG) to control a human–machine interface (HMI) for which the output was vowel synthesis. An auditory-only (AO) group (n=16) trained with auditory feedback alone and an auditory–visual (AV) group (n=16) trained with auditory feedback and progressively-removed visual feedback. Subjects participated in three training sessions and one testing session over 3days. During the testing session they were given novel targets to test auditory–motor generalization. We hypothesized that the auditory–visual group would perform better on the novel set of targets than the group that trained with auditory feedback only. Analysis of variance on the percentage of total targets reached indicated a significant interaction between group and session: individuals in the AV group performed significantly better than those in the AO group during early training sessions (while using visual feedback), but no difference was seen between the two groups during later sessions. Results suggest that augmentative visual feedback during training does not improve auditory–motor performance.

Combined Auditory and Vibrotactile Feedback for Human–Machine-Interface Control

The purpose of this study was to determine the effect of the addition of binary vibrotactile stimulation to continuous auditory feedback (vowel synthesis) for human-machine interface (HMI) control. Sixteen healthy participants controlled facial surface electromyography to achieve 2-D targets (vowels). Eight participants used only real-time auditory feedback to locate targets whereas the other eight participants were additionally alerted to having achieved targets with confirmatory vibrotactile stimulation at the index finger. All participants trained using their assigned feedback modality (auditory alone or combined auditory and vibrotactile) over three sessions on three days and completed a fourth session on the third day using novel targets to assess generalization. Analyses of variance performed on the 1) percentage of targets reached and 2) percentage of trial time at the target revealed a main effect for feedback modality: participants using combined auditory and vibrotactile feedback performed significantly better than those using auditory feedback alone. No effect was found for session or the interaction of feedback modality and session, indicating a successful generalization to novel targets but lack of improvement over training sessions. Future research is necessary to determine the cognitive cost associated with combined auditory and vibrotactile feedback during HMI control.

Non-invasive 3D facial analysis and surface electromyography during functional pre-orthodontic therapy: a preliminary report

Objectives:Functional orthodontic devices can modify oral function thus permitting more adequate growth processes. The assessment of their effects should include both facial morphology and muscle function. This preliminary study investigated whether a preformed functional orthodontic device could induce variations in facial morphology and function along with correction of oral dysfunction in a group of orthodontic patients in the mixed and early permanent dentitions.Material and Methods:The three-dimensional coordinates of 50 facial landmarks (forehead, eyes, nose, cheeks, mouth, jaw and ears) were collected in 10 orthodontic male patients aged 8-13 years, and in 89 healthy reference boys of the same age. Soft tissue facial angles, distances, and ratios were computed. Surface electromyography of the masseter and temporalis muscles was performed, and standardized symmetry, muscular torque and activity were calculated. Soft-tissue facial modifications were analyzed non-invasively before and after a 6-month treatment with a functional device. Comparisons were made with z-scores and paired Student's t-tests.Results:The 6-month treatment stimulated mandibular growth in the anterior and inferior directions, with significant variations in three-dimensional facial divergence and facial convexity. The modifications were larger in the patients than in reference children. In several occasions, the discrepancies relative to the norm became not significant after treatment. No significant variations in standardized muscular activity were found.Conclusions:Preliminary results showed that the continuous and correct use of the functional device induced measurable intraoral (dental arches) and extraoral (face) morphological modifications. The device did not modify the functional equilibrium of the masticatory muscles.

Muscle Activity in the Partially Paralyzed Face After Placement of a Fascial Sling

Neuromuscular re-education (ie, physical therapy) is often the first treatment given to patients with a partial facial paralysis. The purpose of this paper was to examine whether by repositioning and supporting partially paretic muscles with a fascial sling, one could improve facial movement in patients for whom the benefits of physical therapy had plateaued. Six patients with a history of unilateral, partial facial paralysis were assessed using the Facial Grading System (FGS) and surface electromyography (EMG) recordings of facial muscle activity. Automated facial analysis (AFA) was used to measure the facial excursions of the most recent patient. The FGS composite scores indicated improvement following static sling placement in all patients. The FGS subscale scores for voluntary movement indicated that the excursion of facial movement increased in 4 of the 6 patients. Surface EMG data demonstrated increased muscle activity in the zygomaticus major muscle in all patients. AFA demonstrated that following sling placement, the excursion of the lip commissure nearly doubled. The sling procedure, traditionally considered an intervention for improving static symmetry of the face, may also be useful for enhancing movement in some patients with a partial facial paralysis. Additional data, such as measurements provided by AFA, are needed to correlate facial displacement with EMG muscle activity.

Objective assessment of opioid action by facial muscle surface electromyography (SEMG)

1. 1. Activity of the mimetic muscles of the upper face were recorded from awake and anesthetized patients by surface electromyography (SEMG). 2. 2. High amplitude SEMG accompanied ketamine anesthesia and/or the presentation of pain-provoking stimuli. 3. 3. During periods of elevated facial muscle activity, fentanyl or butorphanol decreased SEMG amplitude. 4. 4. The opioid-induced SEMG depression was not consistently associated with either lowered vigilance or analgesia but did provide an objective measure of drug effect.